The present invention relates to a process and an apparatus for the continuous charging of at least one liquid reactant with gas for the production of a foamable, liquid reaction mixture. The gas is dispersed in the reactant by means of a hollow stirrer in a gassing tank. The gas-charged component is then supplied to the other reactant to be mixed therewith.
For the preparation of foams from reactive components (and, in particular, polyurethane foams by the reaction of polyols with isocyanates), it is frequently necessary to disperse gases in a certain proportion in at least one of the reactants before the components are mixed.
We have earlier developed a technique to compare the density of the gassed component with a nominal value and increase or reduce the quantity of gas introduced into the reactant if the density differs from this nominal value (see, German Patent Application P 38 08 082.6). This method fails when small or very small quantities of gas are required to be dispersed in the reactant because the density difference between the gassed component and the ungassed component is then not measurable with sufficient accuracy.
The problem therefore arose of providing a process and apparatus which could be used for dispersing the correct proportion of even minute quantities of gas in at least one of the reactants.